Why do you all want an arena so badly? You got no sports team(s) for it.
It's spelled out pretty good in the initial posts of this thread... but... we'd be a better destination for conference (NCAAB) tournaments... NCAAT regionals... Some of the concerts that skips Baltimore would now come...
The events that are there now, would be better...
Most importantly... a new Arena would be in-conjunction with increasing the size of the convention center.... allowing Baltimore to attract larger conventions (and make use of the Hilton, built for conventions)... those conventions being huge money makers for the City.
Lastly, just because Baltimore is (probably) not currently viable to house the NBA or NHL... if you had an Arena with the requisite amount of skyboxes, it would at-least be theoretically possible (if you could then sell those boxes) at some point in time. (And even if it is not viable now, we should not shut the doors on the idea that it might be in 10-15 years.)
What I want is an arena with at-least 18,500 seats, and skyboxes comparable to the Arenas in Philly and DC.